A parking brake is used to engage a portion of a drivetrain of a vehicle to substantially prevent or inhibit movement of the vehicle when parked. For example, U.S. Pat. No. 6,997,521 relates to a brake system for a vehicle having a parking brake system, a service brake system, and a braking control system. The braking control system is adapted to receive a parking brake signal and a speed signal. When the parking brake signal is received, if the speed signal is greater than a certain value, then the service brake may be engaged. In some instances both the service brake and the parking brake may be engaged if the speed signal is greater than a certain value and/or the parking brake may be engaged if the speed signal is below a certain value.
In another example, U.S. Pat. No. 5,370,449 relates to a parking brake system for applying a hydraulic parking brake using a dual solenoid valve. The dual solenoid valve is configured to move from a park position to a gear select position. When in the park position, pressure is removed from the parking brake to apply the parking brake. An electronic control unit is configured to receive a parking select signal, a speed <3 MPH signal, and sense the pressure in the hydraulic line. If the speed <3 MPH signal and the park select signal are received, the solenoid valve is activated to remove pressure and apply the parking brake. If the speed <3 MPH is not received, then a warning device may be energized. If the ignition is off and park has not been selected, then a park lamp may blink for a period of time. If the ignition is off, but the pressure in the hydraulic line is still high after a period of time, the warning device may be energized.
In still another example, U.S. Pat. No. 5,630,489 relates to a parking brake control system for automating the engagement of spring-applied, pressure-released parking brakes when the vehicle is parked and for preventing the parking brakes from engaging when the vehicle is in motion or not in neutral.
In yet another example, U.S. Pat. No. 6,758,298 relates to a bus door/service brake interlock system. The interlock system includes a foot valve assembly to apply the service brakes when warning lights are activated, the vehicle door is open, and a minimum speed is met. An alarm may be activated when low pressure is detected.
In a further example, U.K. Patent Number GB 2453562 relates to a pneumatic braking system. When pressure is not applied, the parking brake and handbrake systems remain applied and the service brake is not activated. A reset valve is manually operated by an operator to pressurize the pneumatic system once the vehicle is started. When the system is pressurized, the handbrake may be released. A door valve and alarm valve are provided to sound a horn when the door is opened and the parking brake is not applied. The horn remains on even if the door is closed and can only be deactivated by applying the service brake.